System and method for transmitting digital video over an optical fiber

ABSTRACT

A system transmits Digital Video Interface (DVI) signals over a single optical fiber between a video graphics-generating source and a video display device. The system accepts input signals from a conventional DVI transmitter for transmitting video-encoded digital signals to a coarse wavelength division multiplexed (CWDM) optical transmitter. The CWDM optical transmitter produces an optical signal comprised of a multiplexed plurality of optical signals having different wavelengths and outputs this multiplexed optical signal to a single optical fiber. The signal is transmitted over the single optical fiber to a CWDM optical receiver which demultiplexes the signals into a parallel plurality of video encoded optical signals which are each separately received in a corresponding plurality of optical receivers to reproduce the original electrical signals of the DVI transmitter. A conventional DVI receiver converts the encoded video signals into decoded digital video signals that are output to a display device such as an aircraft cockpit display system. The invention permits the transmission of digital video signals over a single optical fiber over greater distances than would otherwise be possible with conventional DVI systems employing copper conductors to conduct electrical signals between the DVI transmitter and the DVI receiver.

FIELD OF THE INVENTION

[0001] This invention relates to systems for transmitting videoinformation to a display device, and more particularly to a system fortransmitting multiplexed optical video signals from a video generatingsource over an optical fiber to a display device.

BACKGROUND OF THE INVENTION

[0002] Transmission of high-speed video from avionic video generators tocockpit displays has heretofore been difficult and costly to implement.One potential solution is the adoption of a commercial-off-the-shelf(COTS) approach. Such an approach would likely save money and improveperformance. One such commercial-off-the-shelf approach would be the useof a Digital Video Interface (DVI). Digital Video Interfaces are wellknown at the present time. They make use of copper conductors that linka DVI transmitter with a DVI receiver and use standardized connectors.However, conventional DVI systems are limited to relatively short linkdistances typically no greater than about five meters. This distance canbe extended to approximately ten meters if the gauge (and the cost andweight) of the copper cables is increased. In aerospace applications,however, it is often necessary to transmit digital video signals over adistance longer than what a standard digital video interface allows.This is especially true on commercial aircraft where digital videosignals may need to be transmitted over distances of up to 30 meters ormore.

[0003] In view of the foregoing, there exists a need for some form ofvideo interface which allows digital video signals to be transmittedover distances greater than that allowed by conventional DVI systemswithout incurring significant additional costs in the way of additionalelectronics components. There is further a need to provide such aninterface which does not require the use of large or very costlyelectronic components which require significant additional space andpower requirements, and which would therefore make such an interfaceunsuitable for use in commercial or military aircraft or other forms ofmobile platforms. Still further, there is a need for such a digitalvideo interface system which can be used with well known andstandardized DVI video generators and DVI connectors.

SUMMARY OF THE INVENTION

[0004] The above and other objects are provided by a digital videointerface system in accordance with preferred embodiments of the presentinvention. In one preferred form, the digital video interface systemcomprises a standard Digital Video Interface (DVI) transmitter, astandard DVI receiver, a multi-wavelength multiplexed opticaltransmitter, a single optical fiber, and a multi-wavelengthdemultiplexed optical receiver. The single optical fiber is coupledbetween the output of the multi-wavelength multiplexed opticaltransmitter and an input of the multi-wavelength demultiplexed opticalreceiver. The multi-wavelength multiplexed optical transmitter receivesa parallel plurality of digital video signals from the DVI transmitter.The DVI receiver receives demultiplexed electrical signals from themulti-wavelength demultiplexed optical receiver.

[0005] In operation, digital video signals are produced by a videographics generating source and output to the input of the DVItransmitter. The DVI transmitter encodes the video signals and outputssame as a plurality of encoded digital video signals to the input of themulti-wavelength multiplexed optical transmitter. The multi-wavelengthmultiplexed optical transmitter produces a corresponding plurality ofoptical signals of different wavelengths which are simultaneouslytransmitted from its output over the optical fiber. Within themulti-wavelength demultiplexed optical receiver, these signals are inputto the demultiplexer and are separated into a parallel plurality ofvideo encoded optical signals. The video encoded optical signals aresubsequently individually received by a plurality of optical receiverswhich output a plurality of video encoded electrical signals. In onepreferred embodiment, the multi-wavelength multiplexer and plurality ofoptical transmitters, and the demultiplexer and plurality of opticalreceivers, comprise coarse wavelength division multiplexing (CWDM)transceivers. The video encoded electrical signals are then decoded bythe DVI receiver. The output of the DVI receiver is then transmitted toa display device.

[0006] Communication over an optical fiber offers greatly extended linkdistance, much lower cable size and weight, and virtually eliminatesproblems with electromagnetic interference. The conventional solution ofpreviously developed systems is to send the plurality of DVI signals toan equal number of optical transmitters, over an equal number of opticalfibers, to an equal number of optical receivers that regenerate theplurality of DVI signals at the input of a DVI receiver. This methodrequires at least four and perhaps seven optical fibers, resulting in amulti-fiber interface.

[0007] The system of the present invention is ideally suited for use inaircraft and other mobile platforms that require extended link distanceand cannot tolerate the weight of heavy cabling. The system of thepresent invention advantageously allows digital video signals to betransmitted over a single optical fiber over distances of up to 100meters, or possibly even greater distances, which would not be possiblewith conventional DVI systems which use copper conductors to transmitelectrical signals thereover. Since the present system employs a singleoptical fiber as the transmitting medium, the plurality of video signalsare further much less susceptible to differential phase delay becausethey all pass through a common medium (i.e., the single optical fiber).

[0008] Further areas of applicability of the present invention willbecome apparent from the detailed description provided hereinafter. Itshould be understood that the detailed description and specificexamples, while indicating the preferred embodiment of the invention,are intended for purposes of illustration only and are not intended tolimit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

[0010]FIG. 1 is a simplified block diagram of a digital video interfacesystem in accordance with a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following description of the preferred embodiment(s) ismerely exemplary in nature and is in no way intended to limit theinvention, its application, or uses.

[0012] Referring to FIG. 1, there is shown a digital video interfacesystem 10 in accordance with a preferred embodiment of the presentinvention. The system 10 generally includes a well-known digital videointerface (DVI) transmitter 12, a well-known multi-wavelengthmultiplexed optical transmitter 14 (hereinafter “optical transmitter14”), a well-known single optical fiber 16, a well-knownmulti-wavelength demultiplexed optical receiver 18 (hereinafter “opticalreceiver 18”) and a well-known DVI receiver 20.

[0013] The DVI transmitter 12 and multi-wavelength multiplexed opticaltransmitter 14 are included within a video generating device 11. The DVItransmitter 12 is comprised of a plurality of encoder/serializercircuits 22 a, 22 b and 22 c which each receive digital video signalsfrom the digital video generating device. Such a device might comprise,for example, an avionic video generator which is generating videosignals for use on a cockpit display of an aircraft. It will beappreciated immediately, however, that the system 10 is not limited touse on aircraft. The system 10 may be used in any application wheredigital video signals need to be transmitted over distances greater thanthat allowed by a conventional DVI system employing copper conductorsbetween the DVI transmitter and DVI receiver. Accordingly, the presentinvention will likely find utility in a variety of aerospace andaeronautical applications, and likely with mobile platforms such asships, buses, submarines or any other form of mobile platform. It isalso likely that the system 10 may be used in land based applicationswhere a video generator needs to be located at some distance from itsassociated video display.

[0014] With further reference to FIG. 1, encoder/serializer 22 areceives a data signal on inputs 24, a horizontal sync signal (HSYNC) oninput 26 and a vertical sync (VSYNC) signal on input 28. Common input 30data enable (DE) is used for enabling or disabling all theencoder/serializers 22 a-c. Similarly, encoder/serializer 22 b receivesa data signal on inputs 32, and control signals on inputs 34 and 36.Encoder/serializer 22 c receives a digital video data signal on input 40while inputs 42 and 44 each receive control signals. The signalsreceived by inputs 24, 32 and 40 represent byte-wide blue, green and reddata signals.

[0015] The output of the DVI transmitter 12 represents encoded digitalvideo signals and a clock signal (CLK) that are applied to drivers 48a-48 d of the optical transmitter 14. In one preferred form, opticaltransmitter 14 comprises a coarse wavelength division multiplexing(CWDM) circuit. The outputs of each of the drivers 48 a-48 d are appliedto a plurality of laser transmitters 50 a-50 d that produce acorresponding plurality of optical signals having different wavelengths.In one preferred form, the lasers 50 a-50 d comprise vertical cavitysurface emitting lasers (VCSEL). In another preferred form, the lasers50 a-50 d may comprise edge-emitting lasers, the choice being dictatedby wavelength and cost. These optical signals having differentwavelengths are output to a multiplexer 52 which transmits the fouroptical signals having different wavelengths simultaneously over theoptical fiber 16.

[0016] The encoded optical signals traveling over optical fiber 16 areinput to a demultiplexer 54 of the optical receiver 18, which in turn ispart of a video display device 21. Receiver 18 also preferably comprisesan array of optical receivers 56 a-56 d, one for each wavelength. Theoptical signals are demultiplexed back into a parallel plurality ofvideo encoded optical signals and applied to optical receivers 56 a-56d. The optical receivers 56 a-56 d convert the video encoded opticalsignals back into a corresponding plurality of video encoded electricalsignals. The output of the optical receiver 18 is then applied to inputs58 a, 60 a and 62 a of a plurality of recovery/decoder circuits 58, 60and 62, respectively. The recovery/decoder circuits 58, 60 and 62 serveto decode the video encoded electrical signals and output these signalsto an inter-channel alignment circuit 64. The inter-channel alignmentcircuit 64 operates to time-align the digital video signal channels andto output aligned digital video signals to a conventional DVI connector,which in turn can be used to couple the signals to the input of acompatible video display device.

[0017] The encoded optical video signals transmitted over the opticalfiber 16 may be transmitted at very high speeds, typically above 1 Gbps.The operation of multiplexing the optical signals and transmitting themover a single optical fiber 16 allows digital video signals to betransmitted over greater distances than would otherwise be possible witha conventional DVI interface system. Importantly, the system 10 of thepresent invention lends itself very well to applications involvingaircraft and other mobile platforms where an avionics bay is typicallylocated a considerable distance from a display unit. It further benefitsfrom the use of commercial-off-the-shelf (COTS) components (i.e., DVIinterfaces and CWDM transceivers) to be employed, which helpsconsiderably to reduce costs.

[0018] While the system 10 has been described in connection with the useof a single optical fiber to convey four DVI interface signals, it willbe appreciated that it could readily be adapted for use with the sevenor more signals required of an upgraded DVI interface.

[0019] Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, specification and following claims.

What is claimed is:
 1. A digital video interface for enablingtransmission of high speed video over extended distances between firstand second video components, said interface comprising: a digital videointerface (DVI) transmitter for encoding video input signals from saidfirst video component to produce a plurality of encoded video signals; amulti-wavelength multiplexed optical transmitter responsive to saidencoded video signals for generating a wavelength multiplexed set ofvideo encoded optical signals encoded with video data; an optical fiberfor receiving and transmitting said multiplexed video encoded opticalsignals; a multi-wavelength demultiplexed optical receiver for receivingsaid multiplexed video encoded optical signals from said optical fiberand demultiplexing said multiplexed video encoded optical signals to aplurality of demultiplexed video encoded optical signals therefrom,which are subsequently converted to video encoded electrical signals;and a DVI receiver for receiving said video encoded electrical signalsand generating therefrom a plurality of decoded digital video signalsfor output to said second video component.
 2. The interface of claim 1,wherein said plurality of demultiplexed encoded video signals comprisesa parallel plurality of video encoded electrical signals.
 3. Theinterface of claim 1, wherein said video encoded optical signals arecomprised of a plurality of different wavelength optical signals.
 4. Theinterface of claim 1, wherein said video encoded optical signalscomprise a plurality of parallel transmitted optical signals.
 5. Theinterface of claim 1, wherein said plurality of decoded digital videosignals comprises a plurality of parallel transmitted decoded videosignals.
 6. The interface of claim 1, wherein one of said video inputsignals comprises a clock signal.
 7. The interface of claim 1, whereinsaid multi-wavelength multiplexed optical transmitter comprises a coarsewavelength division multiplexed optical transmitter element.
 8. Theinterface of claim 1, wherein said multi-wavelength demultiplexedoptical receiver comprises a coarse wavelength division multiplexedoptical receiver element.
 9. A digital video interface system (DVI) forenabling transmission of high-speed video over extended distancesbetween first and second video components, said interface comprising: adigital video interface (DVI) transmitter for encoding video inputsignals from said first video component into a plurality of videoencoded, parallel transmitted signals; a coarse wavelength divisionmultiplexed optical transmitter for converting said video encoded,parallel transmitted signals to a multiplexed, video encoded opticalsignal comprised of a corresponding plurality of optical signals havingdifferent wavelengths; an optical fiber for transmitting saidmultiplexed, video encoded optical signals thereover; a coarsewavelength division demultiplexer for receiving said multiplexed, videoencoded optical signals and generating therefrom a demultiplexedplurality of parallel, video encoded optical signals; and a DVI receivercircuit for receiving said demultiplexed plurality of parallel, videoencoded optical signals and generating therefrom a plurality of decodedvideo signals for driving said second video component.
 10. The interfacesystem of claim 9, wherein said video encoded, parallel transmittedsignals comprise independent blue, green and red encoded video signals.11. The interface system of claim 10, wherein said video encoded,parallel transmitted signals further comprise a clock signal.
 12. Theinterface of claim 9, further comprising an inter-channel alignmentsubsystem for time-aligning said plurality of decoded video signalsprior to transmitting said decoded video signals to said second videocomponent.
 13. A method for transmitting high speed digital videosignals from at least one video generating component to a video displaydevice over an extended distance beyond a distance limit of a standarddigital video interface (DVI) system, the method comprising: using a DVItransmitter to receive a plurality of video input signals from said atleast one video generating component and to generate video encodedelectrical signals; using a plurality of optical transmitters at severalwavelengths to convert the video encoded electrical signals to videoencoded optical signals; using an optical wavelength multiplexer toreceive said video encoded optical signals and to generate therefrom acombined optical signal comprised of said video encoded optical signalseach having different wavelengths and able to travel together on asingle optical fiber; using a single optical fiber to transmit saidcombined optical signal; using a demultiplexer to receive said combinedoptical signal from said optical fiber and to demultiplex said combinedoptical signal to produce a parallel plurality of demultiplexed videoencoded optical signals; using a plurality of optical receivers toconvert the demultiplexed video encoded optical signals to a parallelplurality of demultiplexed video encoded electrical signals; and using aDVI receiver to receive and decode said parallel plurality ofdemultiplexed video encoded electrical signals for subsequent use indriving said video display device.
 14. The method of claim 13, whereinsaid step of using a multi-wavelength multiplexed optical transmittercomprises using a coarse wavelength division multiplexed (CWDM) opticaltransmitter element.
 15. The method of claim 13, wherein said step ofusing a demultiplexed optical receiver comprises using a coarsewavelength division multiplexed (CWDM) optical receiver element.
 16. Themethod of claim 13, wherein the step of using said DVI transmittercomprises generating encoded digital red, green and blue video signals.17. The method of claim 16, wherein the step of using said DVItransmitter to generate said video encoded electrical signals comprisesgenerating an encoded clock signal.